The present invention generally relates to apparatus for separation of solids suspended in a liquid and, more particularly, to an improved lamella-type gravity separator.
Sedimentation basins and clarifiers have been used for many years to separate solids suspended in water and wastewater. They started out as simple concrete or steel tanks where water containing suspended solids flowed in, was retained for a predetermined length of time, and departed, substantially free of suspended solids. Various advancements were made over the years to increase the efficiency of such apparatus; including the incorporation of sludge removal mechanisms, flocculators and sludge recycle mechanisms. More recently, inclined tube settlers of various designs have been installed in such apparatus to increase the surface loading rate.
In recent years the separation art has directed much attention to lamella separation. Lamella separation separates solids from a carrying liquid by directing the liquid between series of inclined plates (lamellae). The effective settling area of each lamella plate is equivalent to the horizontal projection of that lamella plate. Lamella plates are typically spaced a few inches apart, with the result that large settling surfaces are concentrated within a relatively small area. The separated particles settling on the inclined lamella plate slide down into a sludge hopper below the lamella plates. The lamella separation promotes laminar and stable flow conditions throughout the apparatus, which leads to a very high degree of separation.
Lamella separator apparatus are classified into three main categories based on flow regimes in the unit: namely (1) countercurrent, wherein the suspension and the liquid flows are countercurrent to the sludge flow; (2) concurrent, wherein the suspension and the liquid flow are concurrent to the sludge flow; and (3) crosscurrent, wherein the suspension and the liquid flow are at right angles to the sludge flow. As the art has developed, it has been generally recognized that the countercurrent flow regime is the best, as well as the least expensive, both in installation and operation.
In optimizing the design of lamella separator apparatus, there are many design variables which cooperate with one another in determining the efficiency and reliability of the apparatus. These variables include the cooperation between the inlet and outlet assemblies and the lamella plate assemblies. In optimizing these variables, it is desirable to maximize effective use of the projected lamella area, while preventing sludge that has already settled from being re-entrained in the liquid flow. Further, in order to maximize utilization of the lamella settling surfaces and achieve the greatest possible efficiency, it is important that each lamella flow passage be given a substantially equal hydraulic load.
Another important consideration which must be addressed in designing a lamella separator is the ability to maintain the apparatus. Experience has indicated that it is periodically necessary to perform maintenance to the lamella plates and/or to replace them. Accordingly, it is desirable to be able to perform such maintenance and/or replacement without materially interfering with the operation of apparatus.
Examples of heretofore proposed designs of lamella separator apparatus are disclosed in U.S. Pat. Nos. 3,552,554; 3,706,384; 3,894,955; 4,290,898 and 4,681,683. The present invention is directed to improve upon the operational efficiency and the maintenance of such designs.